1/1*2+1/2*3+1/3*4+…+1/99*100=?
1/1*2+1/2*3+1/3*4+…+1/99*100=?
1×2×1/3+2×3×1/4+……98×99×1/100=?
1/1*2+1/2*3+1/3*4+……1/99*100+1/100*101=?坐等,
1/(1+2) + 1/(1+2+3) + 1/(1+2+3+4)……+1/(1+2+3+4+……+99+100)=(
1 2 3 4…… 99 100=?
(-1)+(+2)+(-3)+(+4)+(-5)+……+(-99)+(+100)=?
(+1)+(-2)+(+3)+(-4)+……+(+99)+(-100)=_____
1+2-3+4-……+99-100=?
1/2*1+1*2*3+1/3*4+………+1/99*100
1*2/1+2*3/1+3*4/1+.98*99/1+99*100/1=?
1×2/1+2×3/1+3×4/1……+99×100/1
计算:(1) 1+(-2)+3+(-4)+…+99+(-100) (2)